Safety device for press



L. F. ARCHER SAFETY DEVICE FOR PRESS Filed Aug. 7, 195

INVENTOR. L011 i5 fifl'c er ATTORNEYS.

United States Patent I This invention relates to a safety device for a power press.

A power press of the type of which the present invention is concerned usually has a ram which makes one complete reciprocation at each cycle of operation and then'comes to rest with the ram in the elevated position. The ram is usually driven through a motor belt drive including a clutch mechanism which is pneumatically controlled. A pair of normally closed valves are positioned in the air supply conduit to the press and these are arranged in series so that both valves must be moved to the open position for supplying air pressure to operate the clutch. The valves are manually operated each by a pivoted lever, thus occupying both hands of the operator to move to open relation and providing a desirable safety measure.

It has, however, been found that at times through valve failure and the like, air pressure escaping past the valves will build up in the portion of the conduit leading to the clutch control or the clutch control will otherwise fail and actuate the clutch setting the ram in motion and creating a very serious condition- An object of the invention is to provide a safety device which will operate to provide for a positive arresting of any accident-a1 downward movement of the ram upon valve failure in the air control mechanism of the press.

-Ariother object of the invention is to providea safety device which upon being moved to inoperative position will be reset in ram blocking relation by the downward movement of the ram.

A more specific object of the invention is to provide a safety device wherein a ram blocking means will be arranged in a way to be removed from blocking relation during the manual operation of moving the valves to open position.

With these and other objects in view, the invention consists of certain novel features of construction as will be more fully described and particularly pointed out in the appended claims.

In the accompanying drawings:

1 2 tion type clutch mechanismusually referred to as a dog which automatically becomes disengaged at each revolution to disconnect the drive to the ram. The above drive means is standard, well known to workers in the art, and is no part of the present invention. 'In-the present instance the said clutch is pneumatically controlled and for this purpose the press is provided with an air p'ressure conduit generally designated 18 which leads to the said clutch. A pair of manually operated valves 19', 20 arepositioned in series in conduit 18 and are arranged to be held normally closed. The valve 19 is positioned at one side of the press andthe valve 20 is at the opposite side of the press. The valve 19 controls the air flow to-valve 20 and is manually moved to open position by a lever 21, see Figure 2, which is pivotally mounted as at 22 on a bracket 23 which is also utilized for mounting the valve 19 in place. The lever 21 extends forwardly from the pivot 22 and overlies the stem 19 of the valve'19. The valve is of known type in which the inward movement of the stem 19 will move the valve to open position and will automatically be moved to the closed positionthereof when a force is removed therefrom. Thus upon pressing the lever 21 downwardly about the pivot 22, the lever will engage the stem 19 to move the same inwardly to move the valve 19 to open position so as to open the passageway therethrough to allow aflow of ai-r under pressure from conduit portion 18a to conduitv portion 18b. Upon release of the lever 21, the stem 19' will automatically return to the closed position thereof and also swing lever 21 in the other direction to initial position. p v 7 It will be seen that air pressure will flow to closed valve 20 and be there blocked against passage into conduit portion 180 leading to the said clutch mechanism of the press. The valve 20 is similarly moved to open position by a lever 24 which is similarly swung to engage and move the valve stem 20 to move the valve to open position so as to open the passageway through valve 20 for a flow of air pressurethrough conduit portion 180. 7 It will be apparent from. the above that both valves'19 and 20 need to be movedsimultaneously or nearly so for connecting the ram to the driving means thereof. Thus, moving the valves 19, 20 to open position requires both hands of the operator to be occupied and consequently removed from Figure 1 is a front elevational view of a fragmentary portion of a power press embodying my invention;

Figure 2 is an edge elevation of a fragmentary view of the press of Figure 1; and

Figure 3 is a sectional view taken along line 2-2 of Figure 1 with certain parts omitted for clarity.

Referring to the drawing for a more detailed description of the invention, 10 designates generally a power press, only so much of which has been shown as is believed necessary for a clear understanding of the present invention. The press 10 comprises the usual work shelf 11 which is supported on legs 12. Spaced uprights 13 rise from the shelf 11 and are provided with slides 14 in which a ram 15 is mounted for vertical reciprocation. The shelf provides a support for the lower die portion 16, and the upper die portion 17 is secured to the ram. The ram is operated by known drive means (not shown) which usually includes a motor driven endless belt driving a pulley which is connected to the ram by a one revoluthe vicinity of the dies of the press during the downwardly stroke of the ram.

As previously mentioned, a valve failure such as a leak may occur and cause a very serious and dangerous condition to develop in that pressure builds up in the portion of the air conduit to the ram control to a degree to set the ram in motion. In some instances a failure in valve 19 may allow a pressure to build up in conduit portion 18b and movement of only lever 24 may set the ram in motion. In order to guard against such an event and prevent other uncontrolled downward movements of the ram, I provide an obstruction which is arranged to be held normally in the path of the downward stroke of the ram. The said obstruction in the present instance is a bar or post 25 (see. Figure 3) which is pivotally mounted as at 26 to a block 27 suitably secured to the shelf 11. The post extends vertically with the upper end thereof beneath the ram and closely adjacent the lower edge thereof. Thus unless the post is removed, the same will be engaged by the ram on the downstroke thereof and there held against further movement. A shoulder 28 is provided at the upper end of the post which is biased into engagement with the rear side of the ram by a pull spring 29. One end of the pull spring is fastened to the post 25 as at 30 and the other end of the spring is anchored to a pin or the like 31 held stationary on the plate 11 or at some other suitable location on the press.

A latch 32 is pivotally mounted on post 25 as at 33 and aegeaw extends rearwardly therefrom. The latch is spring biased for counter clockwise rocking (as viewed in the drawing) by a pull spring 35 which is fastened at one end thereof to the latch and at the other end thereof to an anchor pin 36 which project's'fronithe block 27.: A keeper bar 37 projects upwardly Horrible ch27 'inm'enga emem with the lower edge 38 of the latch. Anelon'g'a't'ed'notch orrecess 39 is provided in the edge 38 and extends from. adjacent the pivot 33 to adjacentthe location at which the keeper bar 37 engages the edge 38 when the post25 is in the ram blocking relation. The post 25 may be removed from blocking relationunder proper'control or the operator.

To this end the pivot 22 is extended as at 22' and carries a bell crank 40 having a roller 41 secured'at the free end thereof which extends into engagement with the post 25 as best seen in Figure 3. The pivot 22, to'be hereinafter referred to as a pivot shaft, is fixed to lever 21 and arranged to be rotatable in the bracket 23. 'Thus rocking the lever 21 will also axially turn shaft 22 and rock crank 40 clockwise as seen in Figure 3, roller 41 swinging post 25 out from beneath the lower edge of ram as shown in broken lines. This will carry the latch 32 rearwardly and the keeper bar 37 will ride into the notch 39 and be held engaged against edge 39' through action of spring 35 and pull spring 29. Thus the post will be locked in the inoperative position thereof.

As already mentioned, both hands of the operator will be occupied in pressing down the levers 21 and 24m set the ram in action. Inpractice the operator presses down on both levers simultaneously and then releases the levers prior to the ram completing its cycle of operation. In the inoperative position of the post 25, the forward portion or nose 34 of the latch 32 will be in the path of the down stroke of the ram to be engaged thereby which will rock the latch 32 in the opposite direction and disconnect the notch 39 from the bar 37. Generally, the operator releases levers 21, 24 after the ram has partially com,- pleted its cycle of operation and'therefore roller 41 will be free of the post 25 by the time the ram begins its upward stroke. Accordingly, the pull of spring 29 will be tending to rock post 25 to a vertical attitude and will carry latch 32 to position notch 39 fo'rwardof bar 37.

From the foregoing it will be apparent that post 25 will be held in ram blocking position at all times during inaction of the press so as to block an accidental downward stroke of the ram in the event of valve failure or other cause. Thus the press may be loaded and unloaded in safety at all times. 7 Since operation of the press requires the use of both hands of the operator at a location removed from the path of reciprocation of the ram, post 25 may not be removed by the operator without deliberate knowledge. Thus the operator'will have a' sense of security in operating the press, which is very desirable.

Icl-aim: i V

1. In a pneumatically controlled power press having a ram mounted for vertical reciprocation, an air conduit for said press, a pair of valves in said conduit, said valves being positioned in series in said conduit and normally held closed, a rockable lever for each of said valves 0peratively connected thereto to operate the valves, a bar pivotally mounted on said press in such a manner as to extend generally vertical beneath the rain in position to be engaged thereby to block the downward stroke thereof, a crank connected to one of said levers and extending into engagement with said bar and rockable about an axis parallel to the pivot of said bar by the said levers to Y which it is connected to'move said bar from ram blocking relation, a movable latch carried bysaid bar, and a relatively fixed keeper positioned at a location to engage said latch upon moving said bar from rain blocking relation and retain said bar out of blocking relation, a spring for urging'said bar to ram blocking position, said latch having a portion in the pathof movement of said ram to be engaged by the ram and release the latch from! the keeper after the ram has moved a predetermined distance downwardly. l

2. '-In a pneumatically controlled power press as set forth in claim '1 wherein said latch is spring urgedinto engagement with said keeper.

References Cited in the file of this patent UNITED STATES PATENTS 1,384,348 Riedy Ju1y 12, 1921 1,865,806 Victor July 5, 1932 2,246,021 Sturmet a1. June 17, 1941 2,594,251 Trathen Apr. 22, 1952 2,693,045 John fNov. 2, 1954 

